The scientific focus of the University of Texas Southwestern Medical Center AIDS Clinical Trials Unit (UTSMC ACTU) will be on the immunopathogenesis of HIV infection and immune reconstitution of patients treated with HAART. Specific areas of expertise include the role of the adult thymus in immune reconstitution of patients on HAART, the role of HIV-specific CD4+ and CD8+ T cell responses in the control of HIV replication in patients who are, and are not, treated for HIV infection, and the role of immune activation in HIV immunopathogenesis. In addition, investigators at UTSMC ACTU have extensive expertise in lipodystrophies, which they will bring to the study of protease inhibitor-induced lipodystrophy. Given the strengths in both clinical and basic science, they feel that the proposed UTSMC ACTU will serve as an integral part of the AACTG's mission to develop novel and effective treatments for HIV infection through a better understanding of the mechanisms underlying the pathogenesis of HIV-induced illness. The overall goal of the UTSMC ACTU will be to contribute to the mission of the AACTG. This will involve the enrolling and retention of appropriate patients into clinical trials developed within the framework of the AACTG. These patients will include all members of the diverse population served by the clinical facilities. More importantly, they envision being active participants in the scientific research agenda of the AACTG, and will contribute substantially to its knowledge base and future direction. In order to complete this goal, the specific aims of the UTSMC ACTU will be: (1) to contribute to the HIV disease research agenda; (2) to contribute to the complications of HIV disease research agenda; (3) to contribute to the immunology research agenda; and (4) to contribute to other research agendas.